1. Field of the Invention
This invention relates to cross country pipeline construction and more particularly to a screening apparatus for screening rock and other debris from ditch backfill soil and simultaneously applying the desired screened padding material to a pipeline or cable in a ditch.
To maximize the life of a buried pipeline or cable it is required that the initial covering or burying of a pipeline or cable in a ditch be done with relatively fine earth, namely screened earth from which rocks and other debris have been removed.
A trench containing a line is filled to a given depth with fine screened earth or sand. This screened earth is preferably obtained from the excavated earth normally used in backfilling a ditch. However, in rocky terrain it is necessary that this earth be screened, as mentioned herein above, to remove objectionable material which might damage the buried line if placed in contact therewith in the ditch or trench.
Since the backfill or excavated earth must be used or removed from the trench site, it is highly preferable that this backfill earth be utilized in obtaining the screened earth for initially filling the bottom portion of the trench.
In many locations, the excavated earth is placed along one side parallel with the trench and the opposite side of the trench is used as a working area for the line laying machines or other equipment. In rough terrain, the backfill or excavated earth side of the ditch is sometimes limited in space making it difficult if not impossible for a backfilling machine to operate on that side of the ditch.
This invention provides a screened bottom bucket attached to the end of a boom in backhoe fashion and operated by a prime mover moving along the working side of a ditch.
2. Description of the Prior Art
The prior art is crowded with machines in which their structure requires them to operate on the backfill soil side of the ditch. In plains areas this presents no problem but in rough terrain or mountainous areas it many times is impracticable if not impossible. Of the numerous patents the following are considered most pertinent.
U.S. Pat. No. 3,732,980 issued May 15, 1973 to Evers et al for EARTH MOVING AND SCREENING EQUIPMENT discloses a screen for use on buckets operated by a front end loader or the like. The screen forms the bight portion of an U-shaped frame which straddles the bucket and is moveable to position the screen beneath the bucket when in a soil dumping action and an upward elevated out-of-the-way position when not used for screening. The screen being vibrated when in a soil screening position.
U.S. Pat. No. 4,157,956 issued Jun. 12, 1979 to Robinson for SCREENING BUCKET discloses a two part bucket mounted on the forward end of a prime mover in which the two parts of the bucket are separable to form a downward opening through which soil or other matter picked up by the bucket may be released. A reel wound web mounted rearwardly of the bucket is connected to the forward half thereof and is payed out across the opening formed by spreading the halves apart to screen material falling therethrough when the bucket is in open position. Bucket supporting arms may be intermittently activated to shake the screen and enhance the screening action.
U.S. Pat. No. 3,003,265 issued Oct. 10, 1961 to Lutjens for BUCKET DEVICE discloses a front end loading bucket having a substantially bucket shaped screen frame for covering the bucket open end in which the screen is pivoted to the top open edge of the bucket and normally held in a raised out-of-the-way position until the bucket is filled and then the screen is inverted for finer soil to fall through the bars of the screen.
U.S. Pat. No. 4,664,791 issued May 12, 1987 McClain et al for PADDING MACHINES discloses a carriage mounted laterally of a tractor moving along one side of a ditch containing a pipeline to be padded. The carriage supports a hopper having a vibratory screen at its depending end which screens soil to be placed over the pipe in the ditch. The hopper is periodically filled by a second machine such as a backhoe accompanying the tractor. Screened out material is deposited laterally of the ditch opposite the position of the tractor.
This invention is believed distinct over the above named patents by providing a backhoe operated bucket having its wall area opposite its bucket filling opening removed and a vibrating screen apparatus inserted therein so that when the bucket is filled and disposed with its earth receiving opening upward over a ditch and the screen vibrated screened padding material falls into the ditch.